W126 560 SEL trans shifts harsh
 

So I went under. There is a new vacuum line installed. But the dial thing it attaches too looks like it *might* be factory. It looks like it turns to be adjusted? So I did. No change.

So what could be defective. I thought I recall reading about the trans shifts being vacuum dependent and a part failing. Pics?

With the engine running, do you have vacuum at the modulator on the drivers side of the trans?

I will check. But its a straight line to the intake, so I would think so. The line is new and connections intact. Although odd that the line is new.

Simply having vacuum present at the input to the modulator is no guarantee that it is working. If you have a MityVac or similar attach it directly to the shift modulator and see if it holds a vacuum. If not, that is your problem and it needs to be replaced.

The part is inexpensive (about $35 as I recall) but was difficult to access on my 560SL without a lift. You may have more room on your car.

If its the part the vacuum line goes right too, it seems easy to replace. Guess I will find out.

shift modulator
 

Yes, that's it. There will be almost no fluid loss when you remove it.

After you install
 

the new one, there may be a short period of trial and adjustment until you have the shift characteristics where you like them. Drive, adjust the modulator if necessary, drive, adjust, etc.

Am I correct that adjusting it is as simple as moving that lever? If so and I am getting no change, I am betting its shot then. I will just replace it. I get parts at dealer cost, so no big deal.

Any leak in a vacuum pipe end, or in a A/C pod will also result in harsh shifting as will a old & leaky modulator valve .

mak

Where can I get a modulator. My usual parts guy where I get goodies at cost can not come up with one, even through his import channel.

Right here
 

on this site. Get Phil before he retires.